Effect of Hf-Doped MCrAlY Alloy on the Structure and Properties of Thermally Grown Oxide Layer

The NiCoCrAlY and NiCoCrAlYHf bond layer alloy was prepared by vacuum melting, followed by the deposition of a ZrO2-7%Y2O3 (7YSZ) ceramic coating on its surface using atmospheric plasma spraying. The cyclic oxidation process of the coating was systematically investigated through extensive analytical equipment and first-principles calculations and compared with conventional NiCoCrAlY coatings. It is demonstrated that NiCoCrAlYHf coatings exhibit greater resistance to oxidation and peeling than NiCoCrAlY coatings when thermally cycled at 1050 degrees C in air. The reason for this difference is that Hf doping can reduce the growth rate of the thermally grown oxide (TGO). In addition, the formation of HfO2 in the TGO layer, which delays the phase transition of Al2O3, reduces the growth of internal stresses in the coating and improves the adhesion of the TGO layer and bond strength of the interface. As a result, Hf doping significantly increases the oxidation lifetime of the coating, approximately 8 times that of NiCoCrAlY.